March 16, 2011 11:13:47am
Re: Japan's Unfolding Nuclear Reactor Accident
Right now this is an accident where the vast majority of the released radioactive contamnation is a tropospheric event. It is currently unlike Chernobyl in that none of the releases from Fukushima Daiichi so far have likely had sufficient energy to loft the material into the jet stream. Once material from Chernobyl hit the jet stream it traveled around the globe in about 26 days.
So for now, as long as things in Japan don't degrade further, most of the radioactive contamination will be confined to a relatively small area (100s of square miles, possibly larger). Distribution of released material is entirely dependent upon the weather and I agree that you probably won't see anything in Nepal - in fact, depending on the elevation where you are you are probably being exposed to a higher naturally occurring general radiation level than the people of Japan are, even in the areas where contamination has spread.
It is absolutely essential to understand that potassium iodide (KI) tablets will only protect against thyroid uptake of radioactive iodine-131. KI tabs will do nothing for other radionuclides.
It is also very important to understand the difference between radiation and contamination. The news media is using the terms interchangeably and that is incorrect as they are very different. In short, radiation is the energy emmitted by a radioactive isotope, contamination is the actual radioactive dirt. You can receive radiation exposure without being contaminated - just like a medical or dental xray. You receive a very small dose of radiation exposure but you aren't contaminated.
Radioactive contamination will no doubt be the long term environmental and multi-generational concern as the various compounds work their way into the food chain and water supply.
Radiation readings need to be understood in the context they are used. For example, the rad levels at the gate of the Fukushima Daiichi complex may be inconsequential - compared to the cloud of Iodine 131 you may be standing in, or the particulate Cobalt-60 contamination you are standing in as a steam vent condensed and dropped particulate in the surrounding environment. The rad levels associated with this contamination might be "low", but the risk of ingestion, deposition and long term concentrated exposure to surrounding tissue is not.
Conversely, the emergency response workers combatting the casualty are far less concerned with the contamination levels then they are with the radiation levels. Anti-Contamination clothing, force air respirators, and other PPE offer a great degree of protection against skin and/or internal contamination, but do very little for general radiation.
Since the accident occurred and has unfolded, the news media has been using radiation and contamination interchangeably and there is a significant difference. You must understand the differences and you must understand the context in which you might be exposed to either since the risk mechanisms for radiation or contamination are not the same, nor is one necessarily worse than the other.
- Internal contamination is worse than a short duration exposure to low to moderate whole body radiation levels.
- External skin contamination is generally 'better' than exposure to moderate to high rad levels. As long as the contamination is external, you can decontaminate yourself with simple soap and water.
- Exposure to contamination wearing appropriate protective clothing and equipment is better than exposure to elevated rad levels.
- Exposure to very high radiation levels is almost always worse than contamination. Especially if the dose accumulates or there is an acute exposure to high rad levels. Depending on the rad level, incapacitation due to radiation exposure/poisoning can happen in a matter of minutes, days or months.
- Highly radioactive Internal contamination is about as bad as it can get. Second only to an immediately incapacitating dose or exposure to rad levels approaching LD50/30. (The dose level where 50% of those receiving the exposure wil die of radiation poisoning/complications within 30 days.)
Understanding the difference between radiation and contamination and the risk mechanism for both is essential so you can properly formulate an effective personal response plan BEFORE you are exposed to them.